A cause of death for  Nicholas Brendon , known for being part of the Scooby gang on  Buffy the Vampire Slayer , has been revealed. According to a May 5 report from the Putnam County Coroner’s office obtained by People, Brandon died of atherosclerotic and hypertensive cardiovascular disease, with acute pneumonia and previous myocardial infarction as contributing factors. The “mechanism of death” was 90% blockage right coronary artery. Brendon’s family revealed the actor died March 20 “in his sleep of natural causes.” He was 54. Watch on Deadline In the report, coroner Todd Zeiner said law enforcement at the scene “found no obvious signs of foul play and assisted me with cataloging the scene. Nothing seemed out of place or disturbed.” Brendon played the series regular role of Xander Harris opposite Sarah Michelle Gellar across Buffy the Vampire Slaye r’s seven seasons on The WB and UPN.…